It was only a matter of time. As security filters improve, spam has to find new ways of slipping through email filters. While image spam and PDF file formats are common, audio spam is the latest twist in spam mail. Spammers are now using MP3 file attachments to bypass increasingly sophisticated filters.

The MP3 files appear with names likes justintimberlake.mp3, weddingsong.mp3, beatles.MP3, listentothis.MP3 and bspears.MP3 which entice innocent users to click on the files. They also appear in the form of mobile phone ringtones or answering machine tones. The files range in size from 88KB to 150KB. Audio spam has risen from a virtual unknown to a promising star by dominating ten percent of all spam traffic.

The latest MP3 file that flood inboxes around the world features an eerie and spooky female voice touting the stock of Exit Only, a website operator that runs, which connects auto buyers and sellers via text messages. The stocks of Exit Only are traded on the lower-standard Pink Sheets. Investigations show that the spam originated from phantom servers or hijacked computer networks that had been inadvertently turned into spam-sending machines without the owner’s knowledge.

Like the image spam, the MP3 spam is used to appeal to listeners to invest in a penny stock. When large numbers of investors click on the file, the shares jump in value. The originators of the scheme then dump their shares for a huge profit in what is called the pump-and-dump scheme.